Pivotable feed dog for double chain stitch sewing machines



July 7, 1959 w. IRMSCHER 2,893,337 PIVOTABLE FEED DOG FOR bOUBLE CHAIN STITCH SEWING MACHINES I Filed July 15, 1957 United States Patent PIVOTABLEIFEED DOG FOR DOUBLE CHAIN srrrcn SEWING MACHINES Walter Irmscher, Kaiserslautern, Pfalz, Germany, as-

signor to G. M. Pfalf A.-G., Kaiserslautern, Pfalz, Germany The invention relates to an arrangement for feeding the material in double chain stitch sewing machines of the type having a projecting looper or catch moving transversely of and below the material feed dog member which is secured to the feed dog supporting bar.

In machines of this type the threading of the looper or catch provides difiiculties because the looper ear is not readily accessible when the stich forming components are in operative position. It has been proposed heretofore to make arrangements in the looper drive to position the looper by shifting or withdrawing into a position which is favorable for the threading operation, but measures of this type complicate and increase the costs of the machine and, above all, increase the bulk of the movable masses, thereby increasing the vibratory disturbances as well as wear.

It is an object of the invention to provide an arrangement which facilitates the threading of the looper without changing the looper drive mechanism.

It is a further object of the invention to provide a material feed dog which is pivotally mounted on the material feed dog supporting bar and horizontally movable from its operative position for the looper threading operation to expose the ear of the looper upon removing or swinging out the stitch plate.

In accordance with the invention a flange formed on the material feed dog is provided with a bore adapted to receive a bolt secured to the material feed dog supporting bar and is guided in a groove in said supporting bar in a manner permitting pivotal horizontal movement of the material feed dog while insuring vertical alignment in a unitary structure.

Securing the dog in operative position is effected by means of an interlocking safety catch defined by a spring biased ball and a corresponding recess.

Further objects and advantages of the invention will become apparent from the following description of one practical embodiment of the invention illustrated in the accompanying drawing, in which Fig. 1 is a perspective view of the front end of a double chain stitch sewing machine showing the material advancing member, generally referred to as feed dog, in operative position with the stitch plate swung to the side;

Fig. 2 is a view of the material advancing mechanism taken from the head end of the machine along line II-II of Fig. 3;

Fig. 3 is a top view of the mechanism with the material advancing dog in operative position; and

Fig. 4 shows the dog flung aside of the operative position.

The bed plate 1 of the machine supports the pivotally movable plate 2 in which the stitch plate 3 is embedded. The looper 4 which is mounted for movement transversely of the direction of material feed is held by the looper carrier 6 secured to the looper supporting bar 5. The movements of the material feeding dog 8 which is supported on the dog carrier bar 7 are derived in a known 2 manner from the feeder shaft 9 byway of the pivot 10 and from the feeder lifting shaft 11 by way of pivot link 12 and a thrust bar 13.

The feed dog 8 is provided with a flange 14 having a bore 15 and a socket 16 and it is pivotable about a cylindrical bolt 17 which is secured by means of its thread 18 to the feed dog carrier bar. The socket 16 is guided in a groove 19.

The socket 16 is provided at its circumferential surface with a spherical recess 20 which is engaged by a ball 21 under the pressure of a spring 22 when the feed dog 8 is in the operating position.

Figs. 3 and 4 illustrate that the looper 4 is laid open by simple swinging of the toothed feed dog 8 in clockwise direction to facilitate the threading operation.

The invention can also be used in machines provided with differential material feed, in which event the for ward material feed dog is similarly arranged for pivotal movement.

Having now described my invention with reference to the embodiment illustrated, I do not wish to be limited thereto, but what I desire to protect by Letters Patent of the United States is set forth in the appended claims.

I claim:

1. In a sewing machine of the double chain stitch type having a material feeding mechanism including a feed dog, and a looper supported on a shaft disposed below and movable relative to the material feed dog, said mechanism including a feed dog supporting bar, said feed dog pivotally mounted on said bar and extending generally at right angles to said looper, a vertically extending pivot member rigidly secured to said supporting bar and supporting said feed dog for pivotal movement on said supporting bar, said feed dog being horizontally movable about said pivot member out of its operative position to a position exposing said looper for threading operations.

2. In a sewing machine of the double chain stitch type having a material feeding mechanism including a feed dog, and a looper supported on a shaft disposed below and movable relative to the material feed dog, said mechanism including a feed dog supporting bar, said feed dog pivotally mounted on said bar and extending generally at right angles to said looper, a vertically extending pivot member rigidly secured to said supporting bar and supporting said feed dog for pivotal movement on said supporting bar, said feed dog being horizontally movable about said pivot member out of its operative position to a position exposing said looper for thread ing operations, and being provided with a flange having a bore and presenting a shoulder, and said supporting bar having a groove receiving said shoulder for guiding said feed dog and a bolt extending through said bore into said supporting bar and constituting said pivot member in combination with said supporting bar and said flange.

3. In a sewing machine of the double chain stitch type having a material feeding mechanism including a feed dog, and a looper supported on a shaft disposed below and movable relative to the material feed dog, said mechanism including a feed dog supporting bar, said feed dog pivotally mounted on said bar and extending generally at right angles to said looper, a vertically extending pivot member rigidly secured to said supporting bar and supporting said feed dog for pivotal movement on said supporting bar, said feed dog being horizontally movable about said pivot member out of its operative position to a position exposing said looper for threading operations, and being provided with a flange having a bore and presenting a shoulder, and said supporting bar having a groove receiving said shoulder for guiding said feed dog, a bolt extending through said bore 3 into said supporting bar and constituting said pivot membet in combination with said supporting bar and said flange, and a detent including an interlocking spring biased ball and a recess mounted for cooperating action in said supporting bar" and in said flange for locking said 5 feed dog in operative position.

References Cited in the file of this patent UNITED STATES PATENTS Shanks Feb. 25, 1879 Onderdonk Feb. 23, 1915 Chairman: May 13, 1924 Nelson Nov. 12, 1957 

